This work constitutes a historical and juridical analysis of the legitimacy of ten presently reigning monarchies of Europe. Against each of them, the author applies the classical criteria of dynastic law — principles forged by the European legal tradition over the course of centuries: native birth (indigenat), equality of marriages, dynastic continuity, the lawfulness of the acquisition of power, and conformity to the fundamental principles of succession. At the heart of this inquiry lies a single, sober question: do the modern European dynasties possess lawful grounds to occupy their thrones? Country by country, in measured sequence, the circumstances of their accession to power are examined, together with their dynastic marriages, constitutional reforms, international treaties, and historical precedents. The author arrives at the conclusion that every one of the monarchies examined is tainted by gross violations of the foundational principles of dynastic law.